Sesshōmaru, born of a great demon bloodline, possessed the perfect power that many demons desired. Because of this, he was always composed and confident in his power, displaying a calm, calculating personality at almost all times. The only trait he inherited from his father was fondness towards humans, which didn't manifest until later on in his life. His calmness often kept his thoughts clear of emotional influence.

Otaku Trivia:

1) According to Rumiko Takahashi, Sesshōmaru's name means "killing perfection", though it can also be translated as "the perfect killer/assassin", "circle of destruction" or "complete destruction of life".

2) His mokomoko-sama grows considerably over the course of the manga, going from a relatively small band of fur to a massive bunch of fur that drags behind him as he walks.

3) Early in the manga, he was appearing smiling a lot. As the manga goes on, he hides his emotions and rarely smiles, becoming more like his character is portrayed in the anime.